1. Field of the Invention
This invention relates generally to a vehicle for use in railed transportation systems. More particularly, the invention relates to a self-powered vehicle configured for operation on a monorail.
2. Description of Related Art
Railed transportation systems are well known in the art. Most conventional railways for transportation of people, goods and other resources rely on friction between the drive wheels and rails. Such conventional rail transportation systems may not be suitable for use on steep grades where traction may become a problem. To compensate for the lack of necessary friction, various elaborate multiple-wheeled and spring-loaded friction-based rail transportation systems have been devised, such as those described in U.S. Pat. No. 4,602,567 to Hedström, U.S. Pat. No. 5,069,141 to Ohara et al., U.S. Pat. No. 5,231,933 to DiRosa, U.S. Pat. No. 5,419,260 to Hamilton, U.S. Pat. No. 5,964,159 to Hein, U.S. Pat. No. 6,053,286 to Balmer, U.S. Pat. No. 6,666,147 to Minges and U.S. Patent Application Publication No. 2004/0168605 to Minges. However, these systems are inherently complex mechanical systems.
For applications where steep grades are the norm, railed transportation systems may rely on a toothed rack rail, usually between the running rails in a system known variously as a “cog railway”, a “rack-and-pinion railway” or simply, “rack railway”. Trains operated on a rack railway are generally fitted with one or more cogwheels or pinions that mesh with the rack rail for driving the train along the track. However, such rack railway systems suffer from derailments when the cogwheel slips out of the teeth in the rail rack. Additionally, the rail rack itself is expensive to produce and maintain. Furthermore, switches for rack railways are more complex because of the rail rack.
Alternative approaches to railed transportation systems for steep gradients may rely on other drive mechanisms such as cables and chain-driven systems to pull a car up a track, or to lower it down a track on a steep incline. Examples of conventional cable-driven railed transportation systems include U.S. Pat. No. 3,891,062 to Geneste, U.S. Pat. No. 4,026,388 to Creissels, U.S. Pat. No. 4,534,451 to Peter, U.S. Pat. No. 4,821,845 to DeVaiaris and U.S. Pat. No. 6,739,430 to Hill. Examples of chain-drive mechanisms for railed transportation are disclosed in U.S. Pat. No. 1,838,204 to Wood and U.S. Pat. No. 4,627,517 to Bor. While these cable and chain-driven systems tend to be simpler than the friction-based systems for inclined applications, they do not lend themselves well to applications that include turns and changes in inclination because of the nature of cable and chain-driven drives. More specifically, it is difficult to configure a chain or cable for driving a car over a track having turns and changes in inclination because the force exerted by a chain or cable is linear in nature, thus requiring pulleys and chain wheels for redirection.
Thus, there exists a need in the art for a vehicle that may be independently driven with an electrical motor and that is capable of being used with monorail tracks having a rack for drive traction. It would be advantageous to have such a rail car formed of high strength, lightweight materials. It would also be advantageous to have a rail car capable of self-leveling to adjust for braking, vertical changes and banking into curves.